Italian police have arrested the suspected new head of the Sicilian mafia and 45 other alleged mobsters in a major blow to organised crime on the Mediterranean island, the Government said.

"There is no more room for this type of scum in Italy," Deputy Prime Minister Luigi Di Maio wrote on Instagram.

The previous boss of bosses, Salvatore "Toto" Riina, died in prison last year after spending almost a quarter of a century behind bars for ordering dozens of murders, including those of two of Italy's most celebrated anti-mob prosecutors.

Among those arrested was Settimo Mineo, an 80-year-old jeweller suspected of heading local mafia families in the Sicilian capital Palermo and of being promoted to lead the whole crime group in May, police said.

"The arrests … represent one of the biggest blows inflicted on the mafia by the state. Mineo had been elected 'heir' of Toto Riina after his death," Mr Di Maio added.

A police source said Mr Mineo was elected boss at a meeting of provincial leaders of the Sicilian mafia, known as the Cosa Nostra, on May 29.

It was believed to be the first such gathering of mob families for more than 25 years.

Once all-powerful in Sicily, the world's most famous crime gang has been squeezed over the past two decades, with many bosses put behind bars, businesses sequestered and locals increasingly ready to defy it.

The meeting in May of the Cosa Nostra cupola, or hierarchy, was seen by investigators as a sign the group was looking to rebuild.

"With an extraordinary operation in the Palermo province, the police have dismantled Cosa Nostra's new cupola," Interior Minister Matteo Salvini said on Twitter.

Mineo was sentenced to five years in jail for mafia-related crimes at the so-called "maxi-trial" that ran from 1986 to 1992 and was spearheaded by prosecutors Giovanni Falcone and Paolo Borsellino.

Both Mr Falcone and Mr Borsellino were murdered in 1992 on Riina's orders after verdicts were delivered.

Following their deaths, the state poured resources into the fight against the mob.